In general, the wet processing of an exposed silver halide photosensitive material (to be simply referred to as a photosensitive material, hereinafter) includes a series of steps, typically development, bleach-fixation, and water rinsing for obtaining color images.
Among these steps, the bleaching step is an essential step for producing color images while bleach-fixation is performed either separately as bleaching and fixing steps or simultaneously as a single blix step depending on the type of photosensitive material.
Only a fixing step is required in producing black-and-white images.
Both the bleaching and fixing steps belong to a desilvering step intended for removing unnecessary silver images.
Like other processing solutions, the processing solutions having a desilvering function used in these processing steps, for example, bleaching, blix, and fixer solutions undergo exhaustion or deterioration with the progress of photosensitive material processing and with the lapse of time. One common approach is a system adapted to make up replenisher solution during processing for maintaining the function of the processing solution constant.
In accordance with the recent general demands, environmental maintenance and resource saving are also imposed on the processing of photosensitive materials. It is desirable from an environmental point of view to reduce the amount of processing solutions having a desilvering function such as bleaching, blix and fixer solutions used, especially replenished in the desilvering steps.
Since the desilvering step cannot fully exert its function by processing in a single blix bath, it usually uses two or more baths of bleaching-fixation, bleaching blix, bleaching-blix-fixation and so on, which requires a larger size of apparatus, giving rise to a problem in addition to the increased replenishment.
The blix solution has a problem in processing a minimal quantity of photosensitive material that a bleaching agent in the solution can oxidize a commonly used thiosulfate fixing agent to form sulfides in the processing tank or associated replenishing tank, eventually causing a replenishing pump or circulating pump to be clogged therewith.
In turn, in processing a large quantity of photo sensitive material, the blix solution has other problems of deficient color recovery and poor photographic quality.